Controlling vapor emission in a small engine fuel tank system

ABSTRACT

A fuel vapor emission system for small engine gas tank which does not require redesign or retooling for manufacturing of the tank. A new filler tube has the lower end positioned to cause fuel to rise rapidly in the tube before the tank is full, signaling the operator to stop refueling and maintain a vapor dome in the tank when the filler cap is replaced. A vapor vent valve is disposed in a separate access opening and includes a float operated rollover valve. The vent valve opens when a predetermined positive pressure is reached in the tank; and, a reverse flow vacuum relief valve is disposed in the vent valve. The outlet of the vent valve is intended to be connected to either a storage canister or the engine air inlet.

This is a continuation-in-part of application U.S. Ser. No. 11/017,584filed on Dec. 20, 2004, which is now U.S. Pat. No. ______.

BACKGROUND OF THE INVENTION

The present invention relates to fuel tank systems for small engines ofthe type employed for portable appliances such as portable powergenerating sets, garden tractors, lawn mowers and other such deviceswhere the fuel tank is either mounted on the engine or closely adjacentthereto. Fuel tanks of this type are typically refueled by removing thefiller cap and pouring fuel from a container having a pouring spout, orby pouring from a container and using a funnel.

Small engine fuel systems have recently been subjected to mandatedrequirements for fuel vapor emission control and it has been required toprevent vapor emission from the tank during operation and when theengine is not operating.

Heretofore small engine fuel systems have often employed a tank havingan open vent in the filler cap for providing make-up air in the tank asfuel was withdrawn but which permitted escape of fuel vapor to theatmosphere.

In order to meet the requirement that a fuel tank for a small engine notemit fuel vapor, the filler cap must be sealed to prevent fuel vaporemission. If the filler cap is sealed then other provisions must be madefor admitting make up air to the tank during engine operation.Furthermore, provisions must be made for overpressure relief. Thus, ithas been desired to find a way or means of sealing a small engine fueltank, yet provide for make-up air and over pressure relief and to do soin a cost-effective manner without requiring redesign or retooling ofthe tanks.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a fuel vapor emission control valve inthe tank which controls the flow of fuel vapor through a passageextending exteriorly of the tank and also includes a rollover or upsetvalve preventing liquid fuel from escaping the tank. The vapor ventvalve includes a head valve which retains the vapor in the tank until apredetermined positive pressure is reached; and, the vent valve alsoincludes a reverse flow check valve permitting make-up air to enter thetank as fuel is withdrawn or upon a sub-atmospheric pressure occurringin the tank such as, for example, by cooling of the tank. The fuel vaporvent passage may be connected externally to either a vapor storagedevice or the air inlet of the engine. The invention includes fitting anexisting fuel tank with a filler tube extending to a predetermined levelor depth in the tank to cause the fuel to rise rapidly in the fillertube upon reaching the lower end of the tube during refueling to signalthe operator that tank has reached the desired fill level. Thisarrangement prevents overfilling and preserves a vapor dome in the tankabove the liquid level of the fuel to ensure proper functioning of thevapor vent valve.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial schematic showing a small engine fuel tank incross-section with the filler tube and vapor vent valve of the presentinvention installed thereon; and, the connections to either a vaporstorage device or alternatively the engine air inlet are shown in dashedline;

FIG. 2 is an enlarged detail of the vapor vent valve of FIG. 1;

FIG. 3 is an enlarged view of a portion of FIG. 2 with the vapor ventvalve closed;

FIG. 4 is a view similar to FIG. 3 showing the vapor vent valve opened;and,

FIG. 5 is a view similar to FIG. 3 with the reverse flow valve shownopen in response to a vacuum in the tank.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, the small engine fuel tank assembly of thepresent invention is indicated generally at 10 and includes an existingtank wall structure 12 with a new filler tube 14 having a vapor tightremovable closure 16 received on the exterior end of the tube with thelower end of the tube 14 extending into the tank to a desired depth orlevel indicated by the reference character d.

A separate access opening 18 is formed in the upper portion of the tankwall and through which is inserted a combination rollover and vapor ventvalve indicated generally at 20 which has a lower housing portion 22extending into the tank and an upper housing portion 24 with anoutwardly extending flange 26 thereabout attached to the tank wall andsealed thereabout by any suitable expedient as, for example, weldment.

The lower valve housing 22 has a float 28 disposed therein with aflexible valve member 30 disposed on the upper end of the float whichcloses in the event that fuel rises above the level d due to sloshing,overfilling or the tank becoming severely tipped or inverted, underwhich conditions valve member 30 seats upon a valve seat 32 formed inthe upper housing 24.

The valve seat 32 is formed on the lower end of a vent passage 34 whichcommunicates with an enlarged diameter upper portion 36 whichcommunicates with vent passage 38 which extends outwardly throughattachment fitting 40 which may be formed as part of the upper housing24.

The enlarged diameter portion 36 of the vent passage has slidablyreceived therein a valve member 42 which has a passage 44 therethroughand which has the lower surface 46 thereof configured to seat uponsurface 48 formed in the upper body at the upper end of passage 34. Whenthe valve member 42 is in the lower position shown in FIG. 3 and FIG. 5,flow through passage 34 must transit through passage 44, not theenlarged diameter passage 36.

Valve member 42 has formed therein a valving chamber 50 with a valveseat 52 formed in an inverted position therein on the lower end of theflow passage 54 which communicates with vent passage 38. Chamber 50 hasreceived therein a check valve member 56 which may be in the form of arelatively light weight ball which may be formed of plastic and whichseats on valve set 52 and closes passage 54 when a positive pressureexists in the fuel tank.

With reference to FIGS. 3, 4 and 5, it will be seen that the enlargeddiameter 36, in which valve member 42 slides, has slots or passages 60formed therein to permit passage of vapors for communication withpassage 38 when the valve member 42 is in the upward position and notseated on the seating surface 48.

In operation, with the filler cap 16 removed and the tank refueledthrough filler tube 14, when the level of the fuel reaches the height d,with continued filling a fuel level increases rapidly in the tube 14giving visual notice to the operator that the tank has reached thedesired fill level. After refueling when the filler cap is replaced, thetank is sealed except for vent passage 38 so long as the tank is in theupright position or is not substantially tilted so as to cause floatvalve 30 to close on valve seat 32.

If the vapor pressure in the tank is substantially atmospheric or onlyslightly above, the valve member 42 is seated on seating surface 48 andonly a small amount of vapor can enter the valving chamber 50 and theflow therethrough passage 44 causes ball valve 56 to seat against theseating surface 52 as shown in FIG. 3 preventing escape of vapor. As thevapor pressure increases, valve member 42 is moved upwardly to theposition as shown in FIG. 4 permitting passage of vapor through passages60 into the passage 38; and, as shown in FIG. 1, to either a storagedevice 70 or to the engine air inlet 72.

In the event that the tank is suddenly cooled and the vapor pressure inthe tank drops below atmospheric, creating a vacuum in the tank, ballvalve member 56 drops from its upper seat 52 allowing make-up air toenter the tank. It will be understood that this condition can also occuras fuel is withdrawn from the tank.

The present invention thus provides a simple, relatively low cost andeasy to install technique for modifying an existing small engine fueltank for control of fuel vapor emissions to meet current requirements.The invention combines a filler tube extending in the tank to maintain avapor dome with a vapor vent control/rollover valve to prevent fuelvapor from escaping to the atmosphere upon connection to either astorage device or the engine air inlet.

Although the invention has hereinabove been described with respect tothe illustrated embodiments, it will be understood that the invention iscapable of modification and variation and is limited only by thefollowing claims.

1. A small engine fuel tank vapor emission control system comprising: afuel tank for use with a small engine; a vapor vent valve disposed toreceive vapor from within the tank and including a vent outlet, whereinthe vapor vent valve closes the vent outlet when the fuel level rises toa predetermined level in the tank; a fill level device disposed througha wall of the tank and configured to provide visual notice that the fuelin the tank has reached the predetermined level; and, a normally closedcheck valve disposed to block vapor flow in said vent outlet andoperable to open at a predetermined vapor pressure in the tank.
 2. Thesystem defined in claim 1, wherein the vapor vent valve includes a bleedport bypassing the check valve for permitting a limited flow when thecheck valve is in the normally closed position.
 3. The system defined inclaim 1, wherein the check valve acts as a vacuum relief valve operableupon occurrence of sub-atmospheric pressure in the tank to permitreverse flow of vapor from the canister to the tank.
 4. The systemdefined in claim 1 wherein the check valve is a vacuum relief valve thatincludes a spherical valve member moveable with respect to a valve seatformed in a valving chamber within the vapor vent valve.
 5. The systemdefined in claim 1, wherein said vent outlet is connected to at leastone of a vapor storage device and an engine air inlet.
 6. The systemdefined in claim 1, wherein the fill level device is a lower end of thefiller tube that extends into the tank such that the lower end is closedby liquid fuel rising in the tank during refueling before the vapor ventvalve closes.
 7. A method of controlling vapor emission from a smallengine fuel tank comprising: forming a fuel tank; disposing a vapor ventvalve for communicating fuel vapor in the tank from the valve outlet toa canister and closing the vent valve when fuel in the tank reaches apredetermined level; disposing a fill level device through a wall in thefuel tank, wherein the fill level device is located to respond to liquidfuel rising in the tank to provide visual notice that the fuel in thetank has reached the predetermined level; and, disposing a normallyclosed check valve in the valve outlet of the vent valve to preventvapor flow to one of a canister and an engine air inlet until the vaporpressure reaches a predetermined level above atmospheric pressure. 8.The method defined in claim 7, further comprising the step of forming ableed passage for bypassing the check valve with a limited flow.
 9. Themethod defined in claim 7, further comprising disposing a vacuum reliefvalve and opening the relief valve upon the occurrence ofsub-atmospheric pressure in the tank to permit vapor flow from thecanister to the tank.
 10. The method defined in claim 7, wherein thestep of disposing the fill level device comprises extending one end ofthe filler tube to a desired level of fuel fill in the tank.
 11. Amethod of controlling venting of fuel vapor in a small engine fuel tankcomprising: disposing a filler tube through a wall of the tank andextending one end of the tube to a desired level of fuel fill in thetank, wherein the filler tube is configured to provide visual noticethat the fuel in the tank has reached the desired level of fuel fill;disposing a float operated vent valve in the tank, wherein the ventvalve vents vapor and closes in response to a rising fuel level, andwherein a vapor outlet of the vent valve is connected to at least one ofa storage canister and an engine air inlet; and, disposing a check valvein the vapor outlet of said vent valve to block flow therethrough atvapor pressures less than a predetermined minimum level aboveatmospheric pressure.
 12. The method defined in claim 11, wherein themethod further comprises permitting reverse flow through the check valveupon occurrence of sub-atmospheric pressure in the tank.
 13. The methoddefined in claim 11, wherein said step of disposing a check valveincludes forming a bleed passage bypassing the check valve for limitedbleed flow when the check valve is closed.
 14. A system for maintaininga vapor dome in a small engine fuel tank connected to a vapor storagedevice comprising: a filler tube with one end extending to apredetermined level in the tank and configured to provide visual noticethat a fuel level in the tank has reached the predetermined level,wherein the filler tube is closable by a user operable closure on an endof the filler tube communicating exteriorly of the tank; a conduitdefining a vapor vent path from the tank to the vapor storage device; apressure responsive valve disposed in the vapor vent path and operableto substantially prevent vapor flow when vapor pressure in the tankremains below a predetermined threshold and to substantially permitvapor flow to the vapor storage device when the vapor pressure in thetank reaches the threshold, wherein upon removal of said closure andrefueling through said tube, fuel reaching the predetermined levelcauses fuel to reach different levels in the filler tube and in the tankto provide visual notice of the fill level and preserve a vapor dome inthe tank.
 15. The system defined in claim 14, wherein the pressureresponsive valve includes a valve member that is moveable to closeagainst a valve vent seat to prevent vapor flow, and a bleed passagebypassing the valve member for permitting limited bleed flow.
 16. Thesystem defined in claim 14, wherein the valve member has a sphericalconfiguration.
 17. The system defined in claim 14, wherein the pressureresponsive valve includes a pressure relief valve.
 18. The systemdefined in claim 14, wherein the pressure relief valve includes areverse flow vacuum relief valve.
 19. The system defined in claim 18,further comprising a float operated valve operable to block the ventpath when the fuel level in the tank reaches a full level.